Bison, I've been looking into making a post pounder. What is vibrating one consist of. Never heard of one.
Errin, I was researching it last year. Talked to and emailed surpluscenter. Once I asked them what size would work best with my tractor, they clammed up and said they couldn't help with design.
I've looked at a number of the pto driven ones and the hydraulic ones you can buy or rent.
I was probably trying to go to big with too much torque.
Most I've seen use 8 to 10 gpm pumps and the motors just have a 1/2" shaft so thats not a big motor and not much hp and torque. The speed is proportional to the gpm you pump through a motor. The torque is proportional to the PSI you are using.
Most that I have looked at figure out to be about 50 to 300 auger rpm. The TSC pto auger is around a 3.5 to 1 drive ratio as I recall without digging out my notes with 540 rpm. (I turned one in the store) Figures out at 150 auger rpm but most people run them at idle. 50 rpm would be plenty. The power pole augers the power co. uses may be slower that that. Too fast is an accident waiting to happen. I have an idea what I would buy but need a valve and maybe a flow divider and then find the time to build a 3 point mount for it. Now I think I'd rather build a pile driver to drive posts. I already have a 2 man auger.